Actuators are used in myriad devices and systems. For example, many vehicles including, for example, aircraft, spacecraft, watercraft, and numerous other terrestrial and non-terrestrial vehicles, include one or more actuators to effect the movement of various control surfaces or components. In many applications such as, for example, aircraft flight surface control systems and aircraft thrust reverser actuation systems, the actuators include power drive units, such as motors, that are configured to receive a source of drive power to move an actuator element, and thus the control surfaces or components, to a commanded position. When the control surfaces or components reach the commanded position, the source of drive power may be removed. Thus, many of the actuators that are used include what is sometimes referred to as a no-back device. The no-back device is configured to hold the actuator in position against the load once the actuator has moved the control surface or component to the commanded position.
The types and configurations of no-back devices that are included in actuators vary. One particular type of no-back device that is used is a permanent magnet device. This type of device typically includes one or more permanent magnets that prevent rotation of the actuator power drive unit when the source of drive power is removed. Although this type of no-back device, as well as the various other device types that are currently known, is generally safe, reliable, and robust, these devices do suffer certain drawbacks. For example, the current devices are a continuous supply of magnetic force against drive unit rotation, in at least one rotational direction, that the drive unit may need to overcome each time it is supplied with drive power. As a result, the size of the power drive unit may be larger than what is needed to move the load alone, in order to overcome this magnetic force, which can increase overall actuator and system size, weight, and costs.
Hence, there is a need for a power drive unit no-back device that does not supply magnetic force against drive unit rotation, and/or does not result in increased overall actuator and system size, weight, and/or costs. The present invention addresses at least one or more of these needs.